Jump to content

Tube Power


ROBERTLATHAM1
 Share

Recommended Posts

hello guys !

i just received the specs. on my 1968 harmony 535 head! wow! what a job it was finding anything on this head! anyways the specs state it has 7 tubes (4 dual purpose "what ever that means") 5 of the tubes are 12ax7"s and 2 of the tubes are 6L6GC's now i thought that two 6l6's made 50 watts but the specs state it is 35watts true power and over 75watts peak. is there different wattages to these 6l6 tubes? and if so can i get higher wattage tubes for the head with out damageing the unit?

Edited by ROBERTLATHAM1
Link to comment
Share on other sites

Welcome to the wonderful world of tube amp power ratings - a pair of 6L6s can be configured to produce between 6 watts (Class A, triode mode) and over 50 watts rms, depending on the desired linearity and frequnecy response. It sounds like you've got a 35 watt rms power section - peak power has become increasingly meaningless, especially since car audio has introduced the concept of "instantaneous power", a completely amibiguous system that allows you to rate 100 watt rms amps at over 1 kilowatt. So, to cut this rant short, no, there aren't any special high-power 6L6s, just different circuit configurations for using them.

Did you ever manage to get hold of a schematic for it?

Link to comment
Share on other sites

Besides the fact that the ~audible difference~ between 35W and 50W would barely be noticable, or of any major contribution, anyway. :D

On paper it looks like a noticable difference, but in reality it's not very much at all (in audible terms).

Things like a tight or mushy bass response, point of breakup, smooth or harsh trebles, and the dB sensitivity/cone variety/magnet structure of the speaker would be more important factors to consider than an extra 15W output, it's really a non-item.

Link to comment
Share on other sites

6L6 tube series were used virtually everywhere during that era. I had an old Teisco guitar/bass amp that used them, probably a lot like your Harmony. If they are the original tubes then there is a likely chance that they will need replacing or at the very least have the output voltage biased. Does it work? And if so, any background noise? Some of those old amps can be biased with a simple screw setting. Unfortunately, I was told my Teisco needed resistors soldered in to balance things up, noisy old bugger. :D

Link to comment
Share on other sites

lovekraft

yes i have foound a scheamatic but have not recieved it yet. the guy who has it does all the tweaks for the red stripes who use silvertone very closely related to the harmony.

drak

as for increasing the power for volume there is no need this amp is really loud. i was just under the impression that 2-6l6 produced 50watts no matter what.

southpa

it works great! no noise! but as for the valves needing replacement i dont know? if replaceing the tubes means more volume i dont know that my cabinet will handel any more lmao! im sure that replaceing them would improve the tone though so yes im planning to replace them but i have no idea of what to do other than replace with what came out with. as far as different tubes go ie 6l6 vs el34 and so on dont know the difference!

thanks guys this site is really great and i need to read up on how to donate. would really like to contribute!

Link to comment
Share on other sites

Here are a couple good resources for tubes and general tube amp maintenance. There is some good info about 6L6 tubes and what else you can use as suitable replacements. I would get the two 6L6's tested and see how their relative output voltages match up.

http://www.geofex.com/tubeampfaq/taffram.htm

http://www.canada.com/shopping/frame.aspx?id=243

Link to comment
Share on other sites

Weren't the 6L6's introduced as a substitute for the KT-66's?

I've got a small 15watt single-ended valve head that I built myself that was running on a single 6L6 and I got hold of a KT-66 and re-biased the amp to suit it. The KT-66 is a gorgeous sounding valve but then the 6L6 sounds great too. They definitely have a distinctly different sound from each other though.

ResizeWizard-11.jpg

That's my amp when it had the 6L6 installed and the cover removed.

Amp2 Another picture of my homemade amp.

It's a fantastic sounding amp and although it's only rated at 15watts it's still mega-loud !!!!!

Edited by JTM45
Link to comment
Share on other sites

southpa

wow really great info there! i have been reading for over an hour now and cant get away from it! my brain in on tube overload lmao! i have decided to change my power tubes to the Sovtek 5881WXT as this tube , i think will acomodat my use more readily than the sylvainia that is presently in my power section. i am getting the feeling that the best tactic for finding tone i desire is to just plain expeiriment i.e buy many different tube packages then mix and match until i find what im after!

thax again

robert latham

p.s. i donated today really love this site!

Link to comment
Share on other sites

Weren't the 6L6's introduced as a substitute for the KT-66's?
No, that's backwards - the KT66 is actually a British redesign of the original 6L6, with slightly better linearity and slightly higher power. The 6L6 has been in production since about 1935, and is pretty much the grandaddy of all "modern" beam tetrodes.
Link to comment
Share on other sites

well i was reading on alink that southpa attached (scrooll up) for the rig i use they say that the 5881's are better suited . i dont know but as i said before tubes are a mix and match thing until you find the combo you like.

peace

Link to comment
Share on other sites

Yeah, try as many different types as you can afford - even all 6L6s are not created equal. I'm not a fan of tetrodes in general myself, except for the 6V6, but it's all about available current and personal taste. If you decide that cheap Chinese tubes sound best in your amp (not very likely, but possible), don't let anybody tell you that you've got to use NOS Mullards! :D

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...